Firing circuit

ABSTRACT

A firing circuit for a charge such as a round of ammunition includes a voltage regulated power supply effective to raise the voltage from the supply voltage available in the vehicle, a storage capacitor charged by the power supply, and means for discharging the capacitor through the igniter of the charge. A circuit responsive to the charge level of the capacitor indicates when it is ready and enables operation of a trigger switch to effect the firing. After a short time delay, the capacitor is drained of any residual charges due to the opening of the firing circuit. Also, for a time after initiation of firing, a timing circuit closes a shunt which disables the supply of the current to the capacitor, preventing further charge during this timing interval.

United States Patent 1 l 1 3,788,228

Wilson Jan. 29, 1974 FIRING CIRCUIT Primary Examiner-Benjamin A.Borchelt Assistant Examiner-Thomas H. Webb [75] Inventor: when wllson,Bolmgbmok' Attorney, Agent, or Firm-Paul Fitzpatrick et al. [73]Assignee: General Motors Corporation,

Detroit, Mich. 57 ABSTRACT Filedi 1972 A firing circuit for a chargesuch as a round of ammu- [21 Appl. No: 238,234 nition includes a voltageregulated power supply effective to raise the voltage from the supplyvoltage available in the vehicle, a storage capacitor charged by theUoso t i a 4 t l 0n R, P, 1 f

F42: 11/06, F42; 15/40, l l/OO through the igniter of the charge. Acircuit responsive ld O earch 102/702, 70- 320/l to the charge level ofthe capacitor indicates when it is ready and enables operation of atrigger switch to ef- [56 1 References Cited feet the firing. After ashort time delay, the capacitor UNITED STATES PATENTS is drained of anyresidual charges due to the opening of the firing circuit. Also, for atime after initiation of 3531399 ll/l970 Miller l()2/70.2 A firing atiming Circuit closes a Shunt which disabhes $417306 12/1968 Knak the sul of the current to the ca acitor reventin 3.350 304 10/1967 Erickson320/: pp y p P 8 further charge during this timing interval.

4 Claims, 2 Drawing Figures 7 EQEI 1 IGNITER ,/6' Z a 5\ l 1 POWERSTORAGE a RELAY 2 so PRLY CAPACITOR I (scR) i i I L TRIGGER INHIBITDISCHARGE SW|TCH 1 l i l 1 1 TIMlNG DELAY 1 i /0 1 PAIENIEI] JAN 2 9I914 POWER SUPPLY iNHIBI F FIRING CIRCUIT This invention described andclaimed herein was made in the course of work under a contract with theDepartment of Defense.

DESCRIPTION My invention relates to electrical firing systems. It isparticularly directed to providing surer firing ofelectrically ignitedammunition charges, although the circuit may well have utility for otherpurposes.

The system according to the invention involves charging a capacitor to asubstantial voltage to provide a high energy low impedance source ofenergy to fire the ammunition or the like. Because of the high voltageand energy, firing can be assured notwithstanding oxides, chemicalresidues, corrosion, or contamination resulting from previously firedrounds of ammunition.

The system also includes means for dissipating the stored energy in thecapacitor safely in the event of misfire of of incomplete discharge ofthe condenser during the firing of the round. The system also providesfor automatic recharging of the storage capacitor in preparation for thenext firing.

A desirable feature of this system is a ready circuit arrangement whichindicates the charged condition of the capacitor and prevents firinguntil the capacitor is fully charged.

The principal objects of my invention are to improve the reliability andsafety of circuits or systems for electrically firing ammunition orother charges. A further object is to provide a simple, reliable, andsafe system for charging a capacitor and providing high energy surges ofcurrent. A still further object is to provide such a system whichassures complete discharge of the capacitor upon its actuation andsubsequent automatic recharging.

The nature of my invention and its advantages will be clear to thoseskilled in the art from the succeeding detailed description of itspreferred embodiment.

Referring to the drawings, FIG. I is a schematic diagram of thepreferred system.

FIG. 2 is a wiring diagram of the preferred system.

Referring first to FIG. I for introduction to the de tailed description,the system includes a power supply 2 which receives low voltageunregulated direct current and includes a voltage regulator, aninverter, a step-up transformer, and a rectifier to provide directcurrent at a higher voltage than that available from the source. Thepower supply is connected to charge a large storage capacitor 3 which isconnected to a relay 4, specifically a silicon controlled rectifier(SCR), which controls the discharge of the capacitor to the igniter orelectrical firing device 6 of the round of ammunition. A ready signaldevice 7 signals the fact that the storage capacitor is charged andready, and also provides an enabling signal to a trigger switch 8 whichfires the SCR to discharge the capacitor through the igniter.

The trigger switch also controls through a delay circuit or delay means10 a discharging or drain circuit 1 l which completely discharges thecapacitor in the event that it has not been discharged through theigniter. The trigger switch also sets into operation a timing circuit ormeans 12 which, for a predetermined time after the Operation of thetrigger switch, makes an inhibiting circuit or means 14 effective.Specifically, the inhilbiting means is a shunt which diverts the outputof the power supply and prevents it from charging the storage capacitor.After the cycle of the timing circuit, the power supply is automaticallyeffective to recharge the storage capacitor.

5 With this introduction to the general nature of the system, we mayproceed to the specific circuits shown in FIG. 2 which I deem bestsuited to effect the purposes of my invention.

The system may be energized by the normal electri cal supply circuits ofa vehicle such as a tank or other weapons carrier, represented in FIG. 2by a storage battery 15 which may, for example, have a 24 volt nominaloutput. The battery or D.C. source energizes the power supply 2 whichcomprises a voltage regulator, an inverter, a step up transformer, and arectifier, and which in the described embodiment provides an output of120 volts D.C. The negative terminal of battery I5 is grounded through alead 16. The positive terminal is connected through a lead 18 to theseries circuit of re sistor l9 and Zener diode 20. The Zener diodemaintains a constant 16 volts on the base of a PNP transistor 22, theemitter of which is energized through a resistor 23 from positive line18. The collector of transistor 22 is grounded through a resistor 24.The collector thus is maintained at a constant potential by the Zenerdiode. This potential controls two transistors 26 and 27 arranged in aDarlington configuration which control the potential of the current flowfrom the battery to the inverter. A capacitor 28 connected between theoutput of the Darlington pair and ground acts as a smoothing filter inthe output of the voltage regulation part of the power supply.

This provides a stable voltage on line 34 to two transistors 30 and 31which drive the input to the step-up transformer 32. The emitters oftransistors 30 and 31 are connected to the regulated voltage output line34 and are grounded through a resistor 35. The collectors of thetransistors are grounded through the primary coils 36 of the transformerand the bases of the transistors are grounded through the feedback coils38. This provides a free-running oscillator circuit which powers thetransformer and generates a substantially square wave alternatingcurrent output in the secondary coil 39 of the transformer. The highvoltage A.C. is rectified by four diodes 40 connected in a conventionalbridge rectifier circuit. This provides an approximately I volt D.C.output on positive line 42 and negative line 43. Current flows from line42 through a resistor 44 of 200 ohms and series connected blockingdiodes 46 to a grounded line 47.

While a preferred power supply has been described, it will be understoodthat any stable D.C. source of sufficient potential which may beavailable may be used to power the firing system.

The storage capacitor 3 of 5600 microfarads capacity is connectedbetween line 47 and the negative line 43. Thus, the output of the powersupply serves to charge the capacitor, the charging time being basedupon the time constant of resistor 44 and capacitor 3. As the capacitorcharges, the negative voltage on line 43 increases in the negativedirection.

This voltage signals the charged state of the condenser to the readysignal circuit 7. Line 43 is connected through a resistor 48 and a Zenerdiode 50 to the base of a PNP transistor 51, the emitter of which isenergized from the +24 volt line 18. When the potential differencebetween the +24 volt line and the minus side of the storage capacitorreaches a value deter mined by the breakdown voltage of Zener diode 50,the transistor 5! conducts, energizing a line 52 connected to itscollector. Line 52 energizes a ready signal light 54 connected to groundthrough a diode 55, which indicates that the firing circuit is incondition for use. The diode 54 prevents backward flow of currentthrough light 54 which would interfere with normal circuit functioningbefore capacitor 3 is charged.

Line 52 also provides energizing current to the manu ally operabletrigger switch 8, which is operable to discharge storage condenser 3through the igniter 6. The trigger switch completes a circuit from theline 52, which is positive, through Zener diodes 56 and 58 resistors 59and 60 to the negative bus 43. Resistor 60 is shunted by a filtercapacitor 62. The potential across capacitor 62 is impressed on the gateof a silicon controlled rectifier (SCR) 63 which completes the circuitfrom storage capacitor 3 through the ignition device 6 when its gate isenergized.

The voltage between Zener diodes 56 and 58 is fed through a resistor 66to the delay device which corn prises a timing capacitor 64 connected tothe negative line 43. The potential across capacitor 64 is supplied tothe emitter of a unijunction transistor 67. A Zener diode 68, connectedto line 43 and through a resistor 70 to line 47, provides a controlledpotential to a circuit through resistor 71', the bases of theunijunction transistor, and resistor 72. This potential determines thetrigger point of transistor 67. When capacitor 64 is charged to thispoint, the transistor impresses a voltage spike across resistor 72. Thischarges a filter capacitor 74 and provides turn-on voltage to the gateof an SCR 75. This SCR is connected in series with a resistor 76 acrossthe storage condenser 3 through lines 43 and 47. This thus constitutesthe discharge circuit of drain which dissipates any unused energy instorage capaci tor 3 in the event that the round fired without using allthe energy stored, or in the event of a misfire or faulty round. Oneresult ofdischarging the capacitor is to prevent SCR 63 from remainingturned on in the event of a continuous, non-firing, intermediateresistance load in the circuit to the igniter 6.

The multivibrator timing circuit 12 which prevents recharging of thestorage capacitor during the firing and discharging cycle is shown atthe right side of FIG. 2. The circuit includes a normally conductingtransistor 78 and a normally nonconducting transistor 79. A circuitcomprising a resistor 80, a Zener diode 82, and a capacitor 83 delivercontrolled voltage from lines 42 and 43 to a line 84. The multivibratoris energized from lines 84 and 43. The multivibrator is triggered by asignal on a line 86 which is connected to the energizing circuit for thegate of SCR 63. Line 86 is connected through isolating diode 87 andresistor 88 to the base of transistor 79, the collector of which issupplied through resistor 90 from line 84 and the emitter of which isconnected to line 43. There is also a circuit to the base of transistor79 from line 84 through resistor 91, diode 92, and resistor 88.Transistor 78 has its collector connected to resistor 91, its emitter toline 43, and its base to line 84 through resistor 96 and a diode 95.With transistor 78 conducting, the drop through resistor 9l will holdtransistor 79 turned off.

When SCR 63 is triggered. the voltage pulse sent through line 86 andresistor 88 raises the base potential of transistor 79, causing it toconduct. This effectively ties one terminal ofa capacitor 94 to thenegative line 43. The other terminal of the capacitor is connectedthrough diode 95 to the base of transistor 78. This lowers the potentialon the base of transistor 78, which normally is energized through aresistor 96 and diode 95, so that the transistor 78 turns oft. Thissituation with transistor 79 conducting and transistor 78 nonconductingpersists until capacitor 94 is charged through resistor 96 to a point atwhich the voltage level on the base of 78 again allows it to conduct.When transistor 78 conducts, the drop through resistor 91 turns offtransistor 79, completing the flip-flop cycle.

During the time that transistor 78 is turned off, a transistor 98 isturned on by base drive through resistor 91, a diode 99, and a resistor100. The emitter of transistor 98 is connected to line 43 and itscollector is connected to line 84 through a resistor 102. Withtransistor 98 conducting, the drop through resistor X02 communicatedthrough diode 103, resistor 104, and a line [06 to the base of atransistor 107 turns off transistor 107. This transistor is energized bya circuit from line 42 through resistor 108 and line 109 to thecollector of the transistor, the emitter being connected to line 43.This turns on two transistors 110 and "I, connected as a Darlingtonpair, which provides the inhibiting circuit 14 of FIG. 1. Transistor 110turns on transistor ill which establishes a shunt from the power supplyline 42 through resistor 44 and transistor ill to the negative line 43.As a result, recharging of the storage capacitor is prevented during thepredetermined period of time until timing capacitor 94 charges to apoint at which the multivibrator reverts to its stable condition. Whenthis occurs, the shunt is opened and recharging of the storage capacitorautomatically ensues.

With recharging of the storage capacitor prevented for a definiteperiod, SCRs 63 and are prevented from remaining on after the capacitorhas been dis charged.

Diodes 112 and 114 are provided to protect the baseemitter junctions oftransistors 78 and 79 respectively.

The structure, principles, and mode of operation of the preferredelectrical circuit or system will be clear to those skilled in theelectronic arts from the foregoing description.

However, for whatever informational value it may have, the followingdata as to components of the electrical system is presented. It will, ofcourse, be understood that components may be substituted or modified tosuit particular system requirements or to benefit by developments in theelectronic art.

Transistor Type 'l'ransistor ype 22 ZNll'iZ (i7 ZNlh'IlB 26 2N3'I67 782N699 27 2N3'I7l 79 2N699 3) 2N4399 9H 2N699 3| 2N4399 lil') M1420 5|2N3'I4l ill) M1420 l l l M13029 Resistor Kilohms Watts Resistor KilohmsWatts 19 l H2 72 1 1/4 23 l H2 76 I H) 24 33 1/4 H) 2 35 .005 l 88 I5I12 44 .220 l0 )0 6.8 48 IS l/2 9| 5| H2 59 .47 IM 96 I00 1/2 60 .47 I14I00 lU I12 66 3000 H4 I02 5i H2 70 22 I14 104 IU U2 7| 3.9 l/4 Hit! 47H2 Capacitor Microfarads Volts 5600 I50 28 4.7 5H 62 .22 5O CapacitorMicrufarads Volts 64 .22 50 "I4 .22 St] )4 I2 30 Zener Type 20 IN3024B5t] IN4759 and tN4750 in series 56 IN4761 58 IN476I 68 I N475 l 82IN3033 The diodes 40 constitute a Motorola No. MDA- 942A-6 diode bridge.Other diodes are type IN4005. The SCRs are General Electric C35C.

It will also be clear that the system or circuit is particularly suitedto the requirements of firing circuits for ammunition and other purposesand provides the advantages of safety, reliable operation, automaticrecycling, and other features referred to earlier in the description.

The detailed description of the preferred embodiment of the inventionfor the purpose of explaining the principles thereof is not to beconsidered as limiting or restricting the invention, since manymodifications may be made by the exercise of skill in the art.

I claim:

I. An electrical system for providing a surge of current to a one-shotload at will comprising, in combination, a source of current, a storagecapacitor chargeable from the source, means optionally operable onlyupon attainment of a predetermined capacitor charge level for connectingthe capacitor to the one-shot load for discharge through the load, meansfor connecting the capacitor to an auxiliary load to assure completedischarge of the capacitor effective a predetermined time afterconnection to the load, and means operative to inhibit recharging of thecapacitor for a predetermined time to allow complete discharge andthereafter initiate recharging of the capacitor.

2. An electrical system for providing a surge of current to a one-shotload at will comprising, in combination, a source of current atregulated voltage, a storage capacitor chargeable from the source, meansoptionally operable only upon attainment of a predetermined capacitorcharge level for connecting the capacitor to the load for dischargethrough the load, means for connecting the capacitor to an auxiliaryload to assure complete discharge of the capacitor effective aprudetermined time after connection to the load, and means operative toeffectively disconnect the capacitor from the source during discharge ofthe capacitor and thereafter reconnect the capacitor to the source.

3. An energizing circuit for an igniter for ammunition and the likecomprising, in combination, power supply means; a storage capacitorconnected to the power supply means for charging thereby; means fordetecting a charged condition of the capacitor; relay means operative todischarge the capacitor through a circuit including an igniter; triggerswitchmeans operable by an operator under control of the detecting meansto operate the relay means when the capacitor is charged; draining meansoperable to discharge the capacitor; delay means actuated uponenergization of the igniter effective after a predetermined time tooperate the draining means; inhibiting means operable to disable theconnection from the power supply means to the capacitor; and timingmeans actuated upon energization of the igniter effective to maintainthe inhibiting means effective for a predetermined time greater than thetime delay effected by the delay means.

4. An energizing circuit for an igniter for ammunition and the likecomprising, in combination, a low voltage D.C. source; power supplymeans effective to generate higher voltage D.C. energized by the source;a storage capacitor connected to the power supply means for chargingthereby; indicator means for indicating the charged condition of thecapacitor; relay means operative to discharge the capacitor through acircuit including an igniter; trigger switch means responsive to theindicator means and operable by an operator to operate the relay meanswhen the capacitor is charged; draining means operable to discharge thecapacitor; delay means actuated upon energization of the ignitereffective after a predetermined time to operate the draining means;inhibiting means operable to disable the connection from the powersupply means to the ca pacitor; and timing means actuated uponenergization of the igniter effective to maintain the inhibiting meanseffective for a predetermined time greater than the time delay effectedby the delay means,

'0' 1' k i i

1. An electrical system for providing a surge of current to a one-shotload at will comprising, in combination, a source of current, a storagecapacitor chargeable from the source, means optionally operable onlyupon attainment of a predetermined capacitor charge level for connectingthe capacitor to the oneshot load for discharge through the load, meansfor connecting the capacitor to an auxiliary load to assure completedischarge of the capacitor effective a predetermined time afterconnection to the load, and means operative to inhibit recharging of thecapacitor for a predetermined time to allow complete discharge andthereafter initiate recharging of the capacitor.
 2. An electrical systemfor providing a surge of current to a one-shot load at will comprising,in combination, a source of current at regulated voltage, a storagecapacitor chargeable from the source, means optionally operable onlyupon attainment of a predetermined capacitor charge level for connectingthe capacitor to the load for discharge through the load, means forconnecting the capacitor to an auxiliary load to assure completedischarge of the capacitor effective a predetermined time afterconnection to the load, and means operative to effectively disconnectthe capacitor from the source during discharge of the capacitor andthereafter reconnect the capacitor to the source.
 3. An energizingcircuit for an igniter for ammunition and the like comprising, incombination, power supply means; a storage capacitor connected to thepower supply means for charging thereby; means for detecting a chargedcondition of the capacitor; relay means operative to discharge thecapacitor through a circuit including an igniter; trigger switch meansoperable by an operator under control of the detecting means to operatethe relay means when the capacitor is charged; draining means operableto discharge the capacitor; delay means actuated upon energization ofthe igniter effective after a predetermined time to operate the drainingmeans; inhibiting means operable to disable the connection from thepower supply means to the capacitor; and timing means actuated uponenergization of the igniter effective to maintain the inhibiting meanseffective for a predetermined time greater than the time delay effectedby the delay means.
 4. An energizing circuit for an igniter forammunition and the like comprising, in combination, a low voltage D.C.source; power supply means effective to generate higher voltage D.C.energized by the source; a storage capacitor connected to the powersupply means for charging thereby; indicator means for indicating thecharged condition of the capacitor; relay means operative to dischargethe capacitor through a circuit including an igniter; trigger switchmeans responsive to the indicator means and operable by an operator tooperate the relay means when the capacitor is charged; draining meansoperable to discharge the capacitor; delay means actuated uponenergization of the igniter effective after a predetermined time tooperate the draining means; inhibiting means operable to disable theconnection from the power supply means to the capacitor; and timingmeans actuated upon energIzation of the igniter effective to maintainthe inhibiting means effective for a predetermined time greater than thetime delay effected by the delay means.